Stepping motor



United States Patent "STEPPING MOTOR Duncan N. MacDonald, Arcadia, Calif., assignor, by

This inventionrelates to a direct drive, bi-directional stepping switchmotorv characterized by simplicity of construction, durability and flexibility of use. -A stepping switch motor in accordance with the invention comprises a supporting framework, a drive shaft vjournaled through a wall of the framework, a bank of contacts mounted on an outer face of the wall of the framework, wipers mountedon the outer end of the shaft ,and depending therefrom in engagement with the contacts, a ratchet wheel mounted adjacent the inner end of the shaft, first andsecond electromagnets mounted to the frameworkon opposite sides of the inner end portion of the shaft, first and second armatures pivotally mounted to the framework and respectively in operative association ,with the first and second magnets, first and second pawls pivotally, mounted respectively to the first and second armatures and engageable with the ratchet wheel at respectively opposite extremities of a chord thereof, means operable to load both pawls and armatures, and means operable responsive todisplacement of each armature to open the electrical circuit of the associated electromagnet. .The switch motor has many novel features which result in ease of fabrication and assembly, extremely long life, c0mpactness,- and diversified utility.

As described abovethe wiper assembly is mounted outwardlyof theTSu portingframeWork, i.e. is cantilevered with respectto the framework. This outboard mounting ofthe wipers permits the attachment of a power take-off for-auxiliary devices. Thisarrangement greatly enhances the commercial utility of theswitch without in any way interferingwith itsconventional operation.

' In. a.prefe rred embodiment of the switch motor each of the two armatures is composed ,of two perpendicularly 1 arranged arms and the armature is pivoted to the frame- .work sothatupon displacement the two arms of the armatureniove.in mutuallytransvers directions. One arm of the armature, referred to as the clapper, is so arranged withrespecttothe associated electromagnet as to be actu- .ated ',thereby, while the other, or driving arm, extends parallel ,to the effective axis of the electromagnet and hoirnalltothe axis .of rotation of the ratchet wheel. The ratchet wheelin turn is adjustably supported in the frameworkso asztobe displaceablein a direction normal to its axis Q Citation and generally parallel to the armature. ;By-t;his means the proper spatial relation between the axes of rotationpf the ratchet wheel and armatures may be readily obtained. The armatures in turn are adjustable in a {direction transverse to the .axis of rotation of the ratchet Wheel and parallel to the plane of the wheel to permit of accurate lateral spacing and proper pawl engagement .with :the ratchet wheel.

i .,The switch motor is directly driven, that is, the ratchet .wheel isengagedand displaced by the displacement stroke of a pawl responsive .to'energization of the respective electromagnet. This arrangement is incontrast to actuation upon the retraction stroke of the armature, i.e. after it is released by the magnet as is conventional in some stepping switches. Coupled with this direct drive feature,

2,914,687 Patented Nov. 24, 1959 each of the armatures is provided with a positive ratchet lock means whereby the ratchet wheel is prevented from overdrive on the actuated stroke of the armature. The relative adjustability of the ratchet Wheel and armatures, as above mentioned, becomes important in insuring the proper relationship between the driving pawl, ratchet wheel and armature lock means.

It is necessary in any such switch that the armatures and pawls be spring-loaded, the armatures being loaded in opposition to magnet drive and the pawls in opposition to rotational. displacement by engagement with the ratchet Wheel. conventionally, these elements are separately spring-loaded, which has proved to incur difiicult problems of relative adjustment and to reduce the effective life of the switch because of the greater number of parts subject to deterioration. In the present switch, a single spring member is interconnected between the two annature supported pawls, and the indicated spring-loading of the armatures and the pawls is accomplished by the single spring. This results in accurate loading balance and the single spring replaces the plurality of springs, hence increasing the life expectancy of the switch.

Another feature of the switch motor which improves its utility over conventional stepping switches is the independent coaxial support of the wiper assembly and ratchet Wheel. These elements are mounted on coaxial shafts which, in operation, are interlocked so that rotational displacement of the ratchet wheel effects alike displacement of the wiper. However, the interlock between the shafts is releasable so that the angular position of the wipers and ratchet wheel may be independently adjusted permitting phase adjustment of the wipers.

The foregoing and other features of the invention will be clearly understood from the following detailed description of a stepping motor in accordance with the invention taken in conjunction with the accompanying drawing, in which:

Fig. l is a plan view of a preferred embodiment of the stepping motor of the invention, illustrated as the motor operator in a stepping switch;

Fig. 2 is a partial front elevation of the apparatus of Fig. 1;

Fig. 3 is a transverse section taken on the line 33 of Fig. 1;

Fig. 4 is a longitudinal section taken on the line 44 of Fig. .1;

Fig. Sis an elevation view of one wiper element of the stepping switch; and

Fig. 6 is a partial simplified circuit diagram showing one manner of utilizing the stepping motor.

Referring to the drawing, the elements of the stepping motor are supported on aframework 10 which includes a base 10A and a front wall 10B extending perpendicularly to the base. A secondary framework 12 is supported'on the Wall 1013 of the framework 10 andincludes brackets 12A, 12B extending perpendicularly to the rear face of wall 10B. A pair of electromagnets 13, 14 are mounted respectively .in the brackets 12A, 12B. An armature 15 is pivotally mounted to bracket 12A adjacent magnet 13 and an armature 16 is pivotally mounted to bracket 12B adjacent magnet 14.

As shown most clearly in Fig. 3, armature 16 comprises two perpendicularlydisposed arms 16A, 16B, the arm 16A underlying magnet =14 and beingreferred ,to as the clapper, and the arm 16B extending generallyparallel to the axis-of the magnet and being referred to as the driving arm. At the lowerend of :the arm 16B the armature includes an extension which is pivotally mounted to a support block 18, the support or armature mounting block in turn being mounted to the bracket 12B. To provide proper lateral adjustment of the armature. 16 the support block may be shimmed with respect to the armature arm 16B above pawl 20 and extend outwardly therefrom respectively in opposite directions from both sides of the armature arm. Pin 22 carries a roller 22C held thereon by a nut 24. The pawl 29 includes a tooth 20A extending inwardly from armature 1e, an upwardly extending stop arm 20B and a downwardly extending lever arm 29C, both disposed on opposite sides of the pivot point of the pawl from tooth 20A. Arm 20B of the pawl is adapted to engage against pin 22A to act a limit to the counterclockwise rotation of the pawl as viewed in Fig. 3. This pin has a cammed cylindrical surface by means of which the pawl is adjusted. Armature is identical to armature 16 and supports a pawl 25 likewise identical to pawl 29 and including an inwardly extending tooth 25A, an upwardly extending arm 25B, and a downwardly extending arm 25C, the two arms again being disposed on opposite sides of the pivot point of the pawl from tooth 25A. An armature pin 23 is identical to the pin assembly described in detail in relation to armature 16.

A linear U-shaped spring 26 is connected at its extremities to depending lever arms C and C of the respective pawls. The spring is generally U-shaped with its base extending transversely of the rotational axis of the armatures. As previously mentioned, this spring urges the respectively engaged arms of pawls 20, 25 and also armatures 15 and 16 outwardly, i.e. away from the center plane of the switch.

A support sleeve 28 is cantilevered to and extends through wall 103 of the framework extending rearwardly therefrom generally parallel to the base and perpendicularly to the front wall. The sleeve has a depending flange 28A which is anchored to the frame work 1%) by a screw assembly 288 as illustrated in Fig. 4. The adjustable screw assembly 2813 serves to anchor the sleeve against rotation with respect to the framework, and also serves to make small adjustments of the orientation of the sleeve and the elements connected thereto in the direction normal to the axis of the sleeve. A tubular axle 29 is coaxially mounted within the sleeve extending outwardly from the rear end thereof. A ratchet wheel 3t) is mounted on the projecting end of the axle 29. A shaft 32 is journaled through the tubular axle 29 extending outwardly from the front face of wall 193 and rearwardly of the ratchet wheel 30. Nut 33 holds the wiper assembly on an end of the shaft 32 and nut 34 binds the axle 29 to the shaft so that when thus locked they rotate in unison. However, release of the locking arrangement permits relative rotation of the shaft 32 and axle 29 for the purpose of adjusting the rotational position of one relative to the other.

The ratchet wheel is toothed around its periphery and carries a pair of rearwardly extending pins 36, 37. A spring detent 38 is supported from the secondary framework 12 in engagement with the periphery of the ratchet wheel. The pawls 20 and 25 are in transverse alignment with the ratchet wheel so that pivotal displacement of the respective armatures responsive to energization of the respective electromagnets engages one or the other of the pawls with an aligned tooth of the wheel, displacement of the armature being such that the wheel is driven one step, i.e. through an angular rotation equal to the angle included between the center lines of adjacent teeth for each actuation of the armature. Teeth 16D on armature 16 and the corresponding teeth on armature 15 engage and lock the ratchet wheel at the extremity of armature travel to prevent overdrive of the ratchet. The detent 38 prevents counter-rotation of the ratchet wheel upon retraction of the respective driving pawls.

It is apparent from the drawing that the two armature and pawl assemblies drive the Wheel in opposite directions when separately energized.

To adapt the stepping motor as the motor operator of a stepping switch, a plurality of arcuate arranged banks of contacts 40 are mounted on the front face of framework wall 10B. These contact banks are conventional and any number within the limits of the power capacity the switch may be incorporated.

A plurality of wipers 42, equal in number to the number of contact banks, are mounted on the outboard end of shaft 32 and are insulated from each other and from the shaft by an insulating washer 43. I The wipers are unique in shape and provide at the same time a maximum degree of flexibility and a maximum support at the contact tip. One of the wipers 42 is shown in elevation in Fig. 5 and comprises an annular hub 42A from which a pair of flexible arms 42B, 42C depend supporting a contact tip 42D between the outer extremities. The arms are connected to the hub 42A at their upper extremities ion the opposite side of the hub from the contact tip,

and a continuous slot 42E extends along the extremity of each arm and across the contact tip. A high degree of flexibility is imparted by the slot 42E and by the connection of the arms at the upper part of hub 42A, and extra support of the contact tip is supplied by virtue of disposition thereof between the extremities of the two arms. The slotted tip additionally provides independent twin contact action.

The electrical circuit of an electromagnet is shown schematically in Fig. 6 and includes a number of switches actuated by the respective armatures. The circuit of Fig. 6 is described with relation to'magnet 13 and armature 15 as illustrated in Fig. 3. An input signal is connected across terminals 46, the circuit being closed by a control switch 47 externally of the stepping switch, the control switch 47 being frequently manually operated. The input signal is fed through switch 47 to a dipole switch 48 which includes a bus 48A and spring switch arms 48B, 48C, the switch normally being closed through the arm 48B as illustrated. The arm 48B of switch 48 is connected to a second switch 50 including a bus 50A and spring switch arms 50B, 50C, the connection from switch arm 4813 being to the switch arm 50B of switch 50. The bus 50A of switch 50 is connected through magnet 13 to one of the input terminals.

With switch 47 closed an input signal will energize magnet 13 causing the described displacement of armature 15 whereupon the armature pin 23 releases arm 50C allowing it to make contact with bus 50A and immediately thereafter springing arm 50B to break that contact. The arm 50C acts as a so-called preliminary make-switch preventing ambiguity of armature travel. The loading spring 26 returns the armature to its retracted position and as long as the input signal remains across the terminals 46 the armature will repeat this process, stepping the ratchet wheel at each cycle until pin 37 on the ratchet wheel strikes against bus 48A of the switch 48 and displaces it from the switch arm 48B. This opens the magnet circuit and at the same time closes a circuit through switch arm 48C whereby a signal may be fed from the switch through so-called carry terminals 52 to indicate this condition. The circuit associated with the other magnet 14 is identical, as is the arrangement of the associated switches corresponding to switches 48 and 50 as described.

Rotation of the ratchet wheel responsive to acutation of the respective armatures induces like rotation of the wipers efiecting a step-wise displacement of the wiper contact point along the several arcuately arranged contacts in the contact bank.

I claim:

1. A stepping motor comprising a framework, the

framework including a ;wall having front and rear sides support means with respect to-said wall, a toothed, sprocket wheel disposed coaxially with the ;drive shaft andvlocated to the rear of saidwall, means-rotatablygcoupling the sprocket wheel to the,drivezshaftnmeans:forreleasably fixing the rotary position of the. sprocket twheel irelative to the shaft, first and;secondwelectromagnets disposed to the rear of said wall, the'electrom'agnets:beingconnected to the framework and 'locatedzon opposite sides of the drive shaft proximate to the-sprocket wheel, .first and second armatures pivotally connectedto the'framework adjacent said:electroma-gnets-andoperably associated respectively with the electromagnets, first and second pawl members, and means coupling :the first and second pawl members respectively a to the :first' and second armatures, whereby, pivotal displacement,ofarespective armature in response to energization of the associated electromagnet engages the associated .pawl member with an aligned tooth of the sprocket wheel.

,2. A stepping motoracomprising :a framework, the framework including a ,wallhaving frontand rear sides and a threaded opening extending through :it, a sleeve .member screwed into 'said .threaded opening inthe wall and extending re-arwardlytherefrom, a flange depending from the sleeve member, an adjustable screw assembly coupling the flange tothe'wall forpreventing rotation of the sleeve member-and for making small adjustments of the orientation of the sleeve member along .adirection normalto the axis of the sleeve member, a tubular axle disposed coaxially inside'the sleeve member and extending outwardly from both ends'of the sleeve member, the tubular axle being rotatable withrespect to thesleeve member, a sprocket'wheel having atoothed circumference and connected coaxially to thejtubular axle adjacent the rear end thereof, a drive'shaft disposed coaxially inside ,the tubular axle "and extending, outwardly from both ends ofthe tubular axle, the drive shaft being rotatable .with respect to the tubular axle, means forvreleasably fixing therotary position of the drive shaft with respectto the .tubular axle, first and second electromagnets connected to the framework and disposed beside the sleeve member, the electromagnets being respectively located on opposite sides of the sleeve member and extending downwardly with their axes approximately perpendicular to the axis of the sleeve member, first and second armatures operably associated respectively with the first and second electromagnets, each armature having a clapper portion extending beneath the associated electromagnet and having an arm portion rigidly connected to the clapper portion and extending upwardly from the clapper portion and alongside the electromagnet, means pivotally connecting each armature to the framework so that the pivot axis for each armature is approximatelyparallel to the axis of the sleeve member and is located inwardly from the associated electromagnet, first and second pawl members associated with the first and second armatures and disposed in transverse alignment with the sprocket wheel so that pivotal displacement of a respective armature in response to energization of the associated electromagnet engages the associated pawl member with an aligned tooth of the sprocket wheel, the pawl members being engageable with the sprocket wheel at respective opposite extremities of a chord thereof, each pawl member being pivotally connected to the upper end of the arm portion of its associated armature and including a tooth portion for engaging the sprocket wheel and a stop arm portion and a lever arm portion, at least one tooth extending rigidly from the arm portion of each armature below the pawl members and in alignment with the sprocket wheel for engaging the sprocket wheel and halting further displacement of the sprocket wheel after the associated pawl .of the sprocketwheel being an angular distance approximately equal to the angular spacing between centers of adjacent teeth on the sprocket wheel, first and second cams coupled to the first and second armatures respectively, each cam being disposed near the upper extremity of the arm portion of its associated armature ands-positioned in operative association with the stop arm of-the associated pawl member, saidtcams being adjustable for adjusting the initial orientation of the respective pawl members relative to the sprocket wheel, an elongated spring member supported centrally on the framework and having a pair of upwardly extending arms, the arms of the spring member being engaged respectively with the lever arms of the pawl members and urging both pawl members about their pivot connections with the armature sothat the stop arms ,of the pawl members are urged against said cams and concurrently urging the respective armatures about their pivot connection to the framework in the directionwhich urges the arm portions away from the sprocket wheel, and means'operably responsive to displacement of an armature to open the electrical circuit'of the associatedelectromagnet.

3. Apparatus of claim 2 wherein themeans pivotally connecting each armature to the framework comprises first and second support blocks pivotally connected to the first and second armatures respectively, means releasably coupling said support blocks to the framework, and at least one shim member interposed between one of the support blocks and-the framework whereby the'location of the pivot axis of the associated armature is moved further inwardly from the associatedelectromagnet.

4. Astepping motor comprising a framework, a drive shaft, a sprocket wheelhaving a toothed circumference, means couplingthe sprocket wheel coaxially to the drive shaft, means rotatably journaling the drive shaft-to the framework, first and second electromagnets' connected to the framework and respectively located on opposite sides of the drive shaft, first and second armatures 0perably associated respectively with the first and second electromagnets, means pivotally connecting each armature to the framework, first and second pawl members pivotally connected respectively tothe first and second armatures and engageable with the sprocket wheelat respective opposite extremities-ofa cord-thereof, each pawl member having a toothed portion for engaging the sprocket wheel and a stop arm portion, means urging the pawl members about their pivot connections to the armatures, first and second adjustable cams coupled to the first and second armatures respectively, each cam being positioned in operative association with the stop arm portion of its associated pawl member for adjusting the orientation of the pawl member with respect to the associated armature, whereby pivotal displacement of a respective armature in response to energization of the associated electromagnet engages the associated pawl member with an aligned tooth of the sprocket wheel.

5. A stepping motor comprising a framework, the framework including a wall having front and rear sides and an opening extending through it, a drive shaft, a sprocket wheel, a tubular axle rigidly connected coaxially to the sprocket wheel and disposed coaxially around the drive shaft so that the drive shaft is rotatable with re spect to the tubular axle, a sleeve member disposed coaxially around the tubular axle so that the tubular axle is rotatable with respect to the sleeve member, means connecting the sleeve member to the rear side of said wall and in alignment with said opening with the drive shaft extending through said opening, means for releasably fixing the rotary position of the drive shaft with respect to the tubular axle, first and second electromagnets connected to the framework and respectively located on opposite sides of the drive shaft with their axes approximately perpendicular to the axis of the drive shaft, first and second armatures operably associated respectively with the first and second electromagnets, each armature having a clapper portion extending beneath the associated electromagnet and having an arm portion rigidly connected to the clapper portion and extending upwardly from the clapper portion and alongside the elec-- tromagnet, means pivotally connecting each armature to the framework so that the pivot axis for each armature is approximately parallel to the axis of the drive shaft and is located inwardly from the associated electromagnet, first and second pawl members, and means coupling the first and second pawl members respectively to the arm portions of the first and second armatures, whereby pivotal displacement of a respective armature in response to energization of the associated electromagnet engages the associated pawl member with an aligned tooth of the sprocket wheel.

6; Apparatus of claim 5 wherein the means connecting the sleeve member to the rear side of the wall includes a flange depending from the sleeve member, and an adjustable screw assembly coupling the flange to the wall for making small adjustments of the orientation of the sleeve member in a direction normal to the axis of the sleeve member, whereby the position of the sprocket wheel is adjusted.

7. A stepping motor comprising a framework, a drive shaft, a sprocket wheel, means coupling the sprocket wheel coaxially to the drive shaft, means rotatably journaling the drive shaft to the framework, first and second electromagnets connected to the framework, first and second armatures operably associated respectively with the first and second electromagnets, means pivotally connecting each armature to the framework, first and second rigid driving pawl members pivotally connected respectively to the first and second armatures and engageable with the sprocket wheel at respective opposite extremities of a chord thereof, said pawl members being oriented and positioned on said armatures so that they are out of engagement with the sprocket wheel when the armatures are in their normal retracted position, means urging the pawl members toward the sprocket wheel about their pivot connections to the armatures, and means opposed to said last named means for adjusting the orientation of each driving pawl member laterally with respect to its direction of travel when its respective armature is operated and for adjusting the orientation of the pawl members with respect to-the associated armatures to control the point at which each pawlisengageable with the sprocket wheel. a v

8. Apparatus in accordancewith claim 7 wherein each armature has a clapper portion'extending beneath the associated electromagnet and has an arm portion rigidly connected to the clapper portion and extending upwardly from the clapper portion approximately parallel with the axis of the electromagnet, wherein the means pivotally connecting each armature to the framework is located so that the pivot axis for each armature is approximately parallel to the axis of the drive shaft and is located inwardly from the associatedelectromagnet, wherein each pawl member has a lever arm portion, and wherein the means urging the pawl members toward the sprocket wheel about their pivot connections to the armatures comprises an elongated spring member supported centrally on the framework and oriented approximately parallel to said sprocket wheel, the spring member having a pair of arms extending upwardly on opposite sides of the drive shaft, the arms of the spring member being engaged respectively with the lever arm portions of the pawl members and urging said lever arm portions outwardly away from the drive shaft, thereby urging both pawl members about their pivot connections with the armaturesand concurrently urging the respective armatures away from the sprocket wheel about their pivot connections to the framework.

References Cited in the file of this patent UNITED STATES PATENTS 789,239 Souder May 9, 1905 803,414 Hall et al. Oct. 31, 1905 7 1,001,091 Thomassin Aug. 22, 1911 1,126,084 Reisbach Jan. 26, 1915 1,828,113 Howard Oct. 20, 1931 1,932,020 Lazich Oct. 24, 1933 2,019,177 Dressel et a1 Oct. 29, 1935 2,140,126 Broadwell Dec. 13, 1938 2,428,569 Hunt et al. Oct. 7, 1947 2,501,456 Thias et a1 Mar. 21, 1950 2,525,408 Graybill et al. Oct. 10, 1950 2,638,789 Binks et al May 19, 1953 2,710,896 Grraybill et al. June 14, 1955 

